Application of sequential indicator simulation, sequential Gaussian simulation and flow zone indicator in reservoir-E modelling; Hatch Field Niger Delta Basin, Nigeria

Abstract

The study was carried out with the aim of predicting uncertainty using Sequential Indicator Simulation (SISIM) for lithofacies modelling, sequential Gaussian simulation (SGSIM) for reservoir property modelling and inferring the depositional environment using Flow Zone Indicator (FZI). Five well logs, core analysis data and 3D seismic data were used for the study. Reservoir sand named “Reservoir-E” was correlated across the five wells in the field, and its surface was mapped on the seismic sections from the 3D cube. Petrophysical evaluations revealed average, net to gross, porosity, permeability, the volume of shale, water saturation, hydrocarbon saturation (SH), Reservoir Quality Index (RQI) and FZI as 0.70, 0.29, 2342 mD, 0.158, 0.50, 0.50, 2.44 and 5.62 μm, respectively. Structural interpretations on seismic sections revealed five major faults which trend NE-SW, NW-SE and W-E. A 3D grid with dimension 204 × 120 × 5 = 122,400 was constructed to accommodate our model. Validation of lithofacies models shows a correlation coefficient of 89.43–92.98% for well data and model. The property model shows variability in effective porosity and permeability 0.24 to 0.38 and 560 to 5600 mD. The low amount of SH in well HT-2 and HT-3ST1 is attributed to the presence of baffles with low reservoir quality index with 1.81 and 1.67 for RQI and 5.05 and 5.27 for FZI as compared to well HT-1, HT-4ST1 and HT-5 with RQI of 3.61, 2.71 and 2.41 and FZI of 6.25, 5.85 and 5.66. The environment of deposition is interpreted to be mouth bar-upper shoreface. High porosity and permeability values are linked with high FZI and RQI which are targets for exploitation.